Development of the Welded Bellows for KSTAR Vacuum Vessel

KSTAR 진공용기용 용접 Bellows 개발

Vacuum vessel of the KSTAR(Korea Superconducting Tokamak Advanced Research) tokamak is a fully welded structure with D-shaped cross-section. According to the requirements of the physics design, sixteen horizontal ports, sixteen slanted ports, sixteen baking and cooling ports, and twenty-four top and bottom vertical ports are designed for the diagnostics, plasma heating, vacuum pumping, and baking and cooling. Bellows on these ports are used for flexible components to absorb the relative displacement due to the vacuum vessel thermal expansion and the electromagnetic force between the vacuum vessel and the cryostat ports. Fatigue strength evaluation was performed to decide the dimension of the bellows. In order to assure the quality of the bellows, a prototype bellows for the neutral beam injection port has been fabricated and tested prior to main fabrication. It was conformed that the prototype bellows has sufficient fatigue strength and vacuum reliability in the expected load conditions.